Engines, for example vehicle engines, are being downsized and boosted, which is reducing the available vacuum from the engine. This vacuum has many potential uses, including use by the vehicle brake booster.
One solution to this vacuum shortfall is to install a vacuum pump. Vacuum pumps, however, have a significant cost and weight penalty to the engine, their electric power consumption can require additional alternator capacity, and their inefficiency can hinder fuel economy.
Another solution to generate vacuum is to utilize a Venturi device, either an ejector or an aspirator. An ejector generates vacuum through the Venturi effect when the motive air is taken down stream of the turbocharger compressor or another high pressure source and discharged in a low pressure region. An aspirator generates vacuum through the Venturi effect when the motive air is taken before the throttle, typically at atmospheric pressure, and discharged downstream of the throttle. The problem with presently available Venturi devices is their limitations on the amount of suction mass flow rate, and the amount of engine air they consume.
A need exists for improved designs that increase suction mass flow rate, in particular when the motive flow is a boosted motive flow.